Quantum emulator

Abstract

Quantum emulator The present invention relates to a quantum emulator (10) for emulating the response of a quantum device to commands received by the quantum device, the quantum device comprising a system of quantum objects and a set of hardware elements for manipulating the quantum objects following the reception of commands by the quantum device, the hardware elements having imperfections impacting the manipulations, the quantum emulator (10) being configured to receive an input signal corresponding to a command intended to be sent to the quantum device in order to carry out a manipulation, and to compute an output signal corresponding to an emulated response of the quantum device, the quantum emulator (10) comprising a hardware module (32) configured to represent transfer functions taking into account an imperfection introduced by a hardware element.

1 . A quantum emulator for emulating the response of a quantum device to commands received by the quantum device, the quantum device comprising a system of quantum objects and a set of hardware elements for manipulating the quantum objects following the reception of commands by the quantum device, the hardware elements having imperfections impacting the manipulations, at least one imperfection inducing at least one effect among: losses, time delays, dispersion, time shift and distortion, the quantum emulator being configured to receive an input signal corresponding to a command intended to be sent to the quantum device in order to carry out a manipulation, and to compute an output signal corresponding to an emulated response of the quantum device, the quantum emulator comprising a calculator having access to a memory storing:
 system data relative to characteristics of the system of quantum objects,   hardware data relative to characteristics of the set of hardware elements, the quantum emulator comprising:   a hardware module configured to represent transfer functions describing the set of hardware elements as a function of the hardware data, at least one transfer function taking into account an imperfection introduced by an hardware element and inducing at least one effect among: losses, time delays, dispersion, timeshift and distortion, the input of the hardware module being the input signal and the output being an intermediary signal resulting from the application of the transfer functions to the input signal,   a system module configured to generate a time-dependent model of the Hamiltonian of the system of quantum objects, called Hamiltonian model, as a function of the system data and of the intermediary signal, and   a simulator module configured to compute the output signal as a function of the Hamiltonian model.   
     
     
         2 . The quantum emulator according to  claim 1 , wherein at least a piece of hardware data is obtained from measurements performed on some hardware elements of the quantum device. 
     
     
         3 . The quantum emulator according to  claim 1 , wherein the transfer functions of the hardware module are combined to form a functional representation of the hardware elements and their connections. 
     
     
         4 . The quantum emulator according to  claim 1 , wherein the Hamiltonian model comprises a time-dependent equation depending on a set of time-dependent coefficients-, each time-dependent coefficient (c k (t)) being relative to an operator, each time dependent coefficient (c k (t)) being obtained as a function of the intermediary signal. 
     
     
         5 . The quantum emulator according to  claim 4 , wherein the intermediary signal is composed of intermediary subsignals, each time-dependent coefficient being given by the following relation: 
       
         
           
             
               
                 
                   c 
                   k 
                 
                 ( 
                 t 
                 ) 
               
               = 
               
                 
                   
                     ∑ 
                        
                   
                   j 
                 
                 ⁢ 
                 
                   𝒳 
                   
                     j 
                     ⁢ 
                     k 
                   
                 
                 ⁢ 
                 
                   
                     y 
                     j 
                   
                   ( 
                   t 
                   ) 
                 
               
             
           
         
         Where: 
         c k (t) is the time-dependent coefficient for operator k, 
         y j (t) is the intermediary subsignal j, and 
         X jk  is a tensor relative to the system of quantum objects for the intermediary subsignal y j (t) and the operator k. 
       
     
     
         6 . The quantum emulator according to  claim 4 , wherein the time-dependent equation of the Hamiltonian model is given by the following relation: 
       
         
           
             
               
                 H 
                 ⁡ 
                 ( 
                 t 
                 ) 
               
               = 
               
                 
                   ∑ 
                   k 
                 
                    
                 
                   
                     
                       c 
                       k 
                     
                     ( 
                     t 
                     ) 
                   
                   ⁢ 
                   
                     H 
                     k 
                   
                 
               
             
           
         
         Where: 
         c k (t) is the time-dependent coefficient for operator k, 
         H k  is an operator k relative to the coefficient c k (t), and 
         H(t) is the time-dependent evolution of the Hamiltonian at the output of the system module. 
       
     
     
         7 . The quantum emulator according to  claim 1 , wherein the characteristics of the set of hardware elements stored in the memory are relative to transfer function and/or to cut-off values describing each hardware element. 
     
     
         8 . A quantum emulator according to  claim 1 , wherein at least a characteristic of the system of quantum objects stored in the memory is chosen among transition frequencies, transition matrix elements and interaction strengths. 
     
     
         9 . The quantum emulator according to  claim 1 , wherein the input signal comprises at least one time-dependent waveform. 
     
     
         10 . The quantum emulator according to  claim 1 , wherein the input signal is an analog signal, the quantum emulator comprising an analog to digital converter able to convert the input signal into a numerical signal. 
     
     
         11 . The quantum emulator according to  claim 1 , wherein the simulator module is based on a numerical solver for first order ordinary differential equations, such as an explicit Runge-Kutta method. 
     
     
         12 . The quantum emulator according to  claim 1 , wherein the commands are generated using a control element, the emulated response enabling to optimize the control element and input signals. 
     
     
         13 . The quantum emulator according to  claim 12 , wherein the optimization comprises:
 the modification of the control element as a function of the emulated response, or   the modification of the input signal(s) or of quantum protocol(s) enabling to obtain a desired output signal, or   the validation of the control element as a function of the emulated response and the implementation of the control element on a quantum device.   
     
     
         14 . A method for emulating the response of a quantum device to commands received by the quantum device, the quantum device comprising a system of quantum objects and a set of hardware elements for manipulating the quantum objects following the reception of commands by the quantum device, the hardware elements having imperfections impacting the manipulations, at least one imperfection inducing at least one effect among: losses, time delays, dispersion, time shift and distortion, the method being implemented by the quantum emulator according to  claim 1  and comprising the following steps:
 receiving an input signal corresponding to a signal intended to be sent to the quantum device in order to carry out a manipulation, and 
 determining an output signal resulting from the input signal. 
 
     
     
         15 . The method according to  claim 14 , wherein the method also comprises the steps of:
 generating the input signal using a control element, and   optimizing the control element as a function of the determined output signal resulting from the input signal.